Pressure switch



Oct. 3l, 1961 Filed April l2, 1960 F. W. DWYER EVAL PRESSURE SWITCH |Il'INU 'MMIII um n I 39E 3g zep/ @MVM/340W? Oct. 31, 1961 F. w. DwYER ETAL3,007,017

PRESSURE v,SWITCH Filed April 12, 1960 2 Sheets-Sheet 2 United StatesPatent O 3,007,017 PRESSURE SWITCH Frank Dwyer, Oak Park, Ill., andPhillip W. Dwyer, Michigan City, Ind., assiguors to F. W. Dwyer Mfg.C0., a corporation of Illinois Filed Apr. 12, 1960, Ser. No. 21,818 10Claims. (Cl. 200-83) This invention relates to a huid actuated controlunit responsive to fluid pressure differentials and more particularly isconcerned with a pressure switch unit having a differential pressurecapsule provided with externally mounted switch contacts `actuated fromthe power diaphragm of the capsule by an internally mounted rotatableactuating arm that projects through the capsule to operate theexternally mounted switch contacts.

To provide a pressure switch construction for universal application, itis important that the switch contacts be mounted externally of thepressure capsule in order to isolate these contacts from the tluid towhich the unit is connected. \It has long been a problem to provide anefficient arrangement for carrying motion from -an internally mountedpressure-operated element to externally mounted switch contacts. 'I'heactuating mechanism for carrying motion through the capsule must bemounted in gas-tight relation and should ol'rer a minimum of frictonalresistance to movement. In the past, sealing diaphragme have beenutilized in conjunction with differential pressure capsules, but theseact in opposition to the power diaphragm and impair the sensitivity ofthe unit.

The principal object of the present invention is to provide a pressurecapsule with a gas-tight, low-resistance mounting for an actuating armfor transmitting motion from an internal diaphragm to an externallymounted switch device.

Another object of the invention is to provide a pressure capsule with acalibrated adjustable spring seat mounting for establishing apredetermined spring loading on a fluidpressure actuated diaphragm.

Still another object of the invention is to provide a pressure switch ofthe above-mentioned type-of economical construction that is reliable,accurate, and maintenance free.

lOther objects and advantages of the invention will be apparent duringthe course of the following description.

In the drawings:

FIG. l is a cross-sectional view through a pressure switch unitconstructed in accordance with this invention;

FIG. 2 is a reduced top plan view of the unit of FIG. l;

FIG. 3 is an enlarged perspective view of the actuating arm element ofthe unit;

FIG. 4 is an enlarged sectional view illustrating the mountedrelationship of the actuating arm;

PIG. 5 is lan enlarged detail view of a vcalibrated adjustable mountingfor the diaphragm loading spring; and

FIG. 6 is a view similar to FIG. 5 and indicating a modified calibratedmounting mechanism of modified con struction.

Referring now to the drawings, the fluid-actuated control unit isillustrated in FIG. l as comprising a dilerential pressure capsule,designated generally at 10, having a switch device 11 mounted externallythereon and operably connected to an external portion of an internallymounted actuating arm, -designated in its entirety at 12, that ismovable in response to differential pressure changes occurring in thecapsule.

The capsule is provided with high-pressure and lowpressure connectiontaps 13 and 14, respectively, for connection to selected control pointsof a fluid pressure system while the switch device 11 is provided withcon- 3,007,017 Patented Oct. 31, 1961 ice tacts for connection to asuitable control circuit yfor the uid pressure system.

The differential pressure capsule comprises a casing divided into highpressure and low pressure chambers 15 and 16, respectively, by a movablymounted pressureoperated power diaphragm 17. The casing is comprised ofmating rigid shells 18 and 19 that define the highpressure andlow-pressure chambers, respectively. "The shells are formed with annularmarginal anges 18F and 19F for sealing Aengagement on opposite faces ofthe opposite marginal edges of the diaphragm 17. A gasket 20 is providedbetwen the ange 18F and the diaphragm, and ya peripheral clamping ring21 urges the auges of the shells together to establish a seal.

The high pressure shell 18 has an internal passage IGP communicatingbetween the chamber 15 and the highpressure connection tap 13. Similarlythe low-pressure shell 19 has an internal passage 19P communicatingbetween the chamber 16 and the low pressure connection tap 14.

The diaphragm sheet 17 may be of rubber or other similar tlexiblydistortable material and is provided adjacent its outer marginal edgewith an annular convolution 17C that surrounds and supports the centralbody region of this sheet for accommodating substantially freedisplacement thereof in accordance with the pressure differential actingupon it. A metal wear plate 22 is fixed to the high pressure face of thediaphragm 17 substantially central thereof for contact with theactuating arm 12. A second reinforcement plate 23 is fixed to the 10Wpressure face of the diaphragm and provides -a seat for a calibrationspring 24 that reacts between the low pressure shell 19 and thediaphragm 17 In the arrangement illustrated herein for purposesofdisclosure, the spring 24 is shown as a compression spring and itresists diaphragm movement in a direction away from the actuating arm12. llt will be apparent that a Itension spring could be substituted forresisting diaphragm movement in a direction towards the actuating arm.Obviously, the relationship of the high pressure and low pressurechambers may also be reversed, if desired.

In the lembodiment of the invention illustrated herein for purposes ofdisclosure, the high-pressure shell 18 has a centrally located mountingpocket 30, which, as best shown in FIG. 4, is recessed outwardly fromthe diaphragm 17 and is defined in part by spaced apart wall portions 31and 32. 'I'his mounting pocket 30 is in open communication with thehigh-pressure chamber and each of the wall portions 31 and 32 borderingthe pocket is provided with a bearing socket for rotatably mounting theactuating arm 12. 'Wall portion 31 has an external boss 31B that closesoff the adjacent bearing socket to block leakage from chamber 1S.

As best shown in FIG. 3, the actuating arm 12 has a U-shaped bodyportion including opposed sides 12S and a closed end 12C connecting thesides, with the sides having oppositely outwardly extending lateralprojections 12P journalled to rotate in the bearing sockets. Theprojection 12P that is rotatable in wall portion 32 extends completelytherethrough and has a right-angled external extension 12E forconnection to the pivotally mounted actuating arm 11A of the externallymounted switch device 11.

To complete the substantially frictionless, gas-tight, rotatablemounting -for the actuating arm 12, Ian eyelet 33 is provided on each ofthe axle-like lateral projections 1-2P .to function as thrust collarsthereon and a washer 34 of lubric 4material such as vTetlon is providedon each projection for engagement against the eyelet. The boss 31B ofthe shell 18 provides a closed socket passage through which leakage isimpossible, while the other T socket ypassage is sealed by a rubberO-ring 35 that is press-lit on its axle-like projection. The U-shapedbody of the actuating arm 12 is formed so that when in its mountedrelation within the pocket 31, its sides 12S tend to spread tospring-load the eyelets 33 to act-axially against the Teilon washers.Thisl applies a predetermined compression loading upon the rubber O-ring35 to establish an axial seal against the 'wall portion 32. Thepress-tit mounting relationship of the O-ring establshes a radial sealagainst its axle-like projection 12P to complete the sealing of thebearing socket that opens through -wall portion 32. This arrangementprovides a gas-tight, rotatable mounting for the externally vextendingprojection i12P, while the Teflon washers minimize frictional resistanceto rotation of arm 12. The per- `formance of this dry type bearingarrangement remains constant over the useful life of the switch and itis important to the monitoring function of the control unit that itsfrictional resistance be held to a minimum and be maintained at somepredictable constant value.

VIn order that the actuating arm 12 may respond properly to thepressure-induced diaphragm displacements, the arm is biased by anexternally mounted spring wire coil 36, one end of which is iixed to theextension 12E and the other end of which is engageable with the shell 18to urge the actuating arm in a direction of rotation `for holding itsclosed end 12C in abutting relation to the diaphragm 17.

An outer wall 37 of the mounting pocket carries a lseries of externallytapped, inwardly extending, postlike projections 37P that engage -withmounting screws 38 for the switch device 111. These series ofprojections provide a range of mounting positions for the switch deviceto permit regulation of the dead band or makebreak diterential of theunit. The greater the spacing between the pivot axes of the Varm 11A ofthe switch device and the actuating arm 12, the greater is the travel ofthe diaphragm that is required to accomplish switch actuation, andhence, the greater is the required pressure diiferential. The outer endof the extension 12E has a hooked portion 12H and is also provided witha spring wire coil 39, with one end 39E vof the coil being extendedaboutthe hook portion 12H to provide a loop through which the switch armextends for operative connection to the arm 12.

A protecting shield 40 of angular configuration is provided tosubstantially enclose the delicate switch arm arrangement. This shieldis tted in a groove defined between yadjacent integral guide ribs 18R onthe outer face of the high-pressure shell 18 and is anchored in positionby the mounting screws for the switch 11. A number of insulation shields41, 42 and 43 are shown for protecting the external connection tongues11T for the switch 11.

The low-pressure shell =19 is shown provided centrally thereof with atubular sleeve section 19S extending outwardly away from the diaphragm17 to provide a spring chamber that is in open communication with thelowpressure chamber 16. The spring 24, which extends axially in thischamber, has its outer end engaged in a cup-shaped spring seat 44 thatis threadedly adjustable along the length of the sleeve section 19S todetermine the spring force acting on the 'diaphragm to regulate the setpoint `for switch operation. A rubber ring gasket 45 is provided on theouter face 'of the spring seat 44 and a locking spud 46 is threadedwithin the sleeve section to sealingly compress this gasket 'against thespring seat after the desired spring-loading adjustment has been made.

In the Ialternative embodiment shown in FIG. a calibrated adjustablespring seat mounting is provided wherein the sleeve section 19S is inthe form of a separate cup-shaped member of transparent plastic materialand has an external flange 19F sealed to the shell 19 to surround acentral opening .through which the diaphragm spring 24 projects. Arotatable adjustment rod 48 is extended through the rear wall of the cupmember and along the axis of the spring to threadedly engage theadjustable spring seat 44 which is mounted for floating movement alongthe cup member. A stop shoulder 48S is provided on the rod to ix itsposition axially of the cup. A rubber O-ring 49 encircling the neck ofthe rod and a rubber O-ring 50 encircling the spring seat 44 provide aseal.

In accordance with the invention, indicia Iare provided along the lengthof the cup 19S to define a scale S calibrated in inches of water and asuitable reference mark which may be the O-ring 50 on the spring seat44' indicates the pressure of the set point for switch operation.

Still another arrangement providing a calibrated spring seat mounting isshown in FIG. 6 wherein a cup shaped member 19S is shown sealed to theshell to surround a central opening through which the spring `24- isextended. Again indicia are provided to define a scale S along theexterior face of the member 19S and a rotatable adjustment rod 48projects through the member 19S in threaded relation therewith andcarries an adjustable spring seat 44. To indicate the switch setting, anexternal sleeve 51 is engaged over the head of the rod 48" for axialmovement jointly therewith and its end edge 51E cooperates with thescale S. In this case the member 19S need not be transparent.

The foregoing description and the drawings are given merely to explainand illustrate our invention, and the manner in'which it may beperformed, and the invention is not to be limited thereto, exceptinsofar as the appended claims are so limited since those skilled in theart who have our disclosure before them will be able to makemodifications and variations therein without departing from the scopeand 'spirit of the invention.

We claim:

l. A pressure switch comprising `a diierential pressure capsule having aflexibly distortable partitioning diaphragm providing separate pressurechambers in said capsule, each of said chambers opening through saidcapsule for applying tiuid pressure to opposite sides of said diaphragm,a switch device mounted externally on said capsule, an actuating armmounted internally on said capsule and including a rotatable portionprojecting through said capsule in substantially Africtionless gas tightsealed relation therewith to engage and actuate said switch device upona predetermined movement of said arm, and means for causing saidactuating arm to follow the movements of said diaphragm to transmitmotion from said internal diaphragm to said external switch device andwherein said capsule has an internal pocket defined by spaced apart wallportions that extend generally normal to the plane of said diaphragm,said pocket being in open communication with one of said chambers, eachof said wall portions having a bearing socket, with one of said socketsopening through its wall portion and wherein said actuating armcomprises a U-shaped body portion including opposed sides and a closedend connecting the sides, said sides being provided at their free endswith lateral projections extending outwardly beyond the sides to rotatein said bearing sockets, with the projection that is in said one bearingsocket constituting the said rotatable portion and having afurther'extension externally of said capsule operatively connected tosaid `switch device.

2. The pressure switch of claim 1 wherein each lateral projection ofsaid actuating arm has a thrust collar and a washer of lubric materialbetween the collar and the Iadjacent wall portion and wherein the oneprojection that has an external extension is provided with a rubber O-ring outboard of the washer to establish a seal radially against thesaid last-named projection and axially against the adjacent wallportion.

3. A pressure switch comprising a capsule composed of a pair of mating,rigid shells, a diaphragm spanning said shells-and engagedY therebetweento define separate adja-` cent chambers, each shell having an openingfor external connection to apply differential fluid pressure to saiddiaphragm, a spring in one of said chambers and reacting against saiddiaphragm to urge it in a predetermined direction, a switch devicemounted externally on said capsule, an actuating arm mounted internallyon said capsule and including a rotatable portion projecting throughsaid capsule in substantially frictionless gas tight sealed rela tiontherewith to engage and actuate said switch device upon a predeterminedmovement of said arm, and means for causing said actuating arrn tofollow the movements of said diaphragm to said external switch device.

4. A pressure switch comprising a casing composed of a pair of mating,rigid shells, a diaphragm spanning said shells and engaged therebetweento define separate adjacent chambers, each shell having an opening forexternal connection to apply fluid pressure to said diaphragm, a switchdevice mounted on said casing, means including an actuating arm mountedon said casing to follow the movement of said diaphragm and connected tosaid switch device for actuating the same in response to a predeterminedmovement of said diaphragm, one of said shells having a tubular sleevesection centrally thereof and extending outwardly from said diaphragm toprovide a spring chamber opening into the pressure chamber defined bythe said one shell, a spring in said spring chamber to react directlyagainst said diaphragm, and means threadedly engaged with said sleevesection to provide an adjustable seat for said spring for setting thedifferential pressure loading required for actuation of said diaphragm.

5. A pressure switch comprising a casing composed of a pair of mating,rigid shells, a diaphragm spanning said shells and engaged therebetweento define separate adjacent chambers, each shell having an opening forexternal connection to apply fluid pressure to said diaphragm, a switchdevice mounted on said casing, means including an actuating arm mountedon said casing to follow the movement of said diaphragm and connected tosaid switch device for actuating the same in response to a predeterminedmovement of said diaphragm, one of said shells having a tubular sleevesection centrally thereof and extending outwardly from said diaphragm toprovide a spring chamber opening into the pressure chamber defined bythe said one shell, a spring in said spring chamber to react directlyagainst said diaphragm, a yspring seat movable lengthwise in said sleevesection, means for adjusting and maintaining the axial position of saidspring seat in said sleeve section, means defining a scale along saidsleeve section, and means providing an indicator for cooperation withsaid scale, said indicator being movable axially conjointly with saidspring seat.

6. In a pressure switch that includes a differential pressure capsulehaving a flexibly, distortable internal diaphragm defining separatepressure chambers within said capsule, 'an external switch device infixed relation to said capsule and an actuating arm engageable with saiddiaphragm and connected to operate said switch mech- -anism in responseto predetermined deflection of said diaphragm, the improvement 'whereinsaid switch device is externally mounted on said capsule and whereinsaid capsule has spaced apart wall portions defining a mounting pocketwith said wall portions having cooperating bearing sockets, one of whichopens through said capsule and wherein said actuating arm comprises aU-shaped body portion including opposed sides and a closed endconnecting the sides, said sides being provided at their free ends withlateral projections extending outwardly beyond the sides to rotate insaid bearing sockets, with the projecting that is in said one bearingsocket constituting the said rotatable portion and having a furtherextension externally of said capsule operatively connected to saidswitch device.

y7. In a pressure switch that includes a differential pressure capsulehaving a flexibly, distortable internal diaphragm defining separatepressure chambers within said capsule, a switch mechanism and anactuating arm engageable with said diaphragm and connected to operatesaid switch mechanism in response to predetermined deflection of saiddiaphragm, the improvement wherein said capsule comprises mating rigidcasing shells cooperable to grip said diaphragm therebetween, one ofsaid shells having a tubular sleeve section centrally thereof andextending outwardly from said diaphragm to provide a spring chamberopening into the pressure chamber defined by the said one shell, aspring in said spring chamber to react directly against said diaphragm,and means threadedly engaged with said sleeve section to provide anadjustable seat -for said spring -for setting the difierential pressureloading required lfor actuation of said diaphragm, the other of saidshells having a mounting pocket centrally thereof and defined :by spacedapart wall portions of said other shell, and an actuating arm engageablewith said diaphragm and connected to operate said switch mechanism inresponse to predetermined deflection of said diaphragm, the improvementwherein said switch device is externally mounted on said capsule andwherein said capsule has spaced apart wall portions defining a mountingpocket with said wall portions having cooperating bearing sockets, oneof which opens through said capsule and wherein said actuating armcomprises a U- shaped body portion including opposed sides and a closedend connecting the sides, said sides being provided at their free endswith lateral projections extending outwardly beyond the sides to rotatein said bearing sockets, with the projection that is in said one bearingsocket constituting the said rotatable portion and having a furtherextension externally of said capsule operatively connected to saidswitch device.

8. A pressure switch comprising a capsule composed of a pair of mating,rigid shells, a diaphragm spanning said shells and engaged therebetweento define separate adjacent chambers, each shell having an opening forexternal connection to apply differential fluid pressure to saiddiaphragm, a spring in one of said chambers and reacting against saiddiaphragm to urge it in a predetermined direction, one of said shellshaving a series of switch-mounting positions, a switch device forexternal mounting on said one shell and having a pivotally mountedswitch arm, an actuating arm mounted internally on said one shell andincluding a rotatable portion projecting through said capsule forAconnection to the pivotally mounted arm of said switch device, meansfor connecting said actuating Iarm in operative engagement with saidswitch arm, means for biasing said actuating varm for following themovements of said diaphragm to transmit motion from said diaphragm tosaid switch arm, and means for securing said switch device at anyselected one of said positions to vary the dead band of said pressureswitch.

9. A pressure switch comprising a differential pressure capsule having afiexibly distortable partitioning diaphragm providing separate pressurechambers in said capsule, each of said chambers opening through saidcapsule for applying ttiuid pressure to opposite sides of saiddiaphragm, said capsule having a series of external switch mountingpositions, a switch device for external mounting on said capsule andincluding a switch operating arm, an actuating arm mounted internally ofsaid capsule and including a rotatable portion projecting through saidcapsule for engagement with said switch operating arm, means forconnecting said actuating arm in operative engagement with said switcharm means for causing said actuating arm to follow the movements of saiddiaphragm to transmit motion from said diaphragm to said switchoperating arm and means for securing said switch device at any selectedone of said positions to vary the dead band of said pressure switch.

l0. A pressure switch comprising a differential pressure capsule havinga flexible distortable partitioning diaphragm providing separatepressure chambers in said capsule, each of'said chambers opening throughsaid capsule for applying uid pressure to opposite sides of saiddiaphragm, a switch devicer mounted on said capsule, means including anactuating arm mounted on said casing to follow the movement of saiddiaphragm and connected to said switch device for actuating the same inresponse to la predetermined movement of said diaphragm, said capsulehaving a tubular sleeve section extending away from said diaphragm andproviding a spring chamber opening into one of said pressure chambers, aspring in said spring chamber tovreact directly yagainst said diaphragm,and means threadedly engaged with said sleeve section to provideanadjustable seat for said spring for setting the diierential pressureloading required for actuation of said diaphragm.

References Cited in the tile of this patent UNITED STATES PATENTS1,459,218 Knaak June 19, 1923 UNITED STATES PATENT oEEICE CERTIFICATE OECORRECTION Patent No. 3OO7,017 October 31V 196 Frank W. Dwyer et al.

It is hereby certified that error appears in the above numbered patentrequiring correction and that the said Letters Patent should read ascorrected below.

Column line l after "diaphragm" insert to transmit motion from saidinternal diaphragm m,

signed and sealed this 10th day of April 1962.

(SEAL) Attest:

ERNEST W. SINIDEB.

Attesting Officer DAVID L. LADD Commissioner of Patents UNITED STATESPATENT OFFICE CERTIFICATE OF CORRECTION Patent No. BYOOT ,017 October 3lu 196 Frank W. Dwyer et al.

It is hereby certified that error appears in the above numbered patentrequiring correction and that the said Letters Patent should read ascorrected below Column line IEMl after "diaphragm" insert -w to transmitmotion from said internal diaphragm n signed and sealed this 10th dy ofApril 1962.-.

(SEAL) Attest:

ERNEST wy. SWTDEE Attesting Officer DAVID L. LADD Commissioner ofPatents

